The overall goal of the Skeletal Phenotyping Core is to provide the highest quality assessment of skeletal characteristics in the most efficient manner. The core will provide investigators with access to state-of-the-art technology, training in use of new devices (as appropriate) and consultation on experimental design, data analysis and interpretation. Specifically, the core facilities and services will include: 1) peripheral dual-energy X-ray absorptiometry for in vivo assessment of bone mineral density and body composition in mice; 2) histology and histomorphometry, including in situ hybridization and immunohistochemistry; and 3) high resolution micro-computed tomographic (CT) imaging for 3D, non-destructive assessment of bone microarchitecture and morphology. By maintaining bone assessments within the core facility, high quality control standards can be readily maintained. By coordinating the bone analysis efforts, it will be possible, for example, to evaluate the same specimens first with mu CT (which is non-destructive) and then by histology and/or histomorphometry, thereby reducing the number of animals required for each experiment and enhancing the quality of data collected. The core will support Projects III, IV and V of the Program Project. However, it should be noted that establishment of this core will also serve many other investigators in the Endocrine Unit who have projects outside the Program Project. These investigators will have access to the core facilities and services, but will pay for these services in separate agreements with different fee structures than those provided to investigators within the Program Project.